CN117396615A

CN117396615A - High-efficiency energy-saving pyrometallurgical method for treating Li-ion battery

Info

Publication number: CN117396615A
Application number: CN202280037177.1A
Authority: CN
Inventors: 伦纳特·舍尔尼斯
Original assignee: Umicore NV SA
Current assignee: Umicore NV SA
Priority date: 2021-05-26
Filing date: 2022-05-24
Publication date: 2024-01-12
Also published as: CL2023003498A1; JP2024520450A; BR112023024678A2; CA3221381A1; CL2023003499A1; EP4347902A1; AU2022280352A1; MX2023013981A; TW202336239A; US11661638B2; US20220403483A1; WO2022248245A1; TW202319551A; KR20240013192A; WO2022248436A1; US20230250511A1

Abstract

The present disclosure relates to a 2-step smelting process for recovering Ni and Co from batteries and other sources. The method comprises the following steps: -defining an oxidation level Ox and a metallurgical feed comprising a cell; by injecting O-containing into the melt ₂ Oxidizing smelting the metallurgical feed material with a gas to a defined oxidation level Ox; and-reducing the slag obtained from the smelting using a heat source and a reducing agent. The process is more energy efficient than a single step reduction smelting process and provides a higher purity alloy and cleaner final slag.

Description

High-efficiency energy-saving pyrometallurgical method for treating Li-ion battery

The present invention relates to a process for recovering valuable metals such as Ni and Co from batteries and other sources. Ni-Co alloys and slag are produced.

In recent years, electric vehicles have experienced unprecedented growth driven by new laws in europe and china, designed to gradually reduce CO in automobiles ₂ Emissions and limit air pollution in cities. Expected to be inThis growth continues during the next decades. The adoption of electric vehicles depends to a large extent on the performance of the battery used to store the electric energy. In order to obtain the highest energy density while keeping costs controlled, li-ion batteries are used. Many of these cells contain positive electrodes based on the transition metals Ni, mn and Co and are therefore also called NMC cells. As the market for electric vehicles grows, the demand for these metals is expected to increase significantly.

The demands for Ni and Co may even exceed global production capacity. Co is particularly critical because it is only produced today as a by-product of the Ni and Cu industries. The Ni market is significantly larger than the Co market. Most Ni is used to produce stainless steel, where purity is relatively unimportant. However, high purity Ni and Co metals or compounds have been in short supply. In view of the above, recovery of Ni and Co from scrapped batteries is an attractive proposal.

A number of smelting processes have been proposed that allow for the recovery of metal from scrap batteries. Such processes typically produce alloys and slag. The alloy, if sufficiently pure, may be suitable for use, for example, in preparing positive electrode materials for Li-ion batteries, thereby achieving closed loops. Slag may be suitable for use in the construction industry or for safe disposal if it is sufficiently depleted of heavy metals.

However, obtaining pure alloy and highly depleted slag while conserving energy is challenging.

In europe, classification, marking and packaging (CLP) regulations EC n° 1272/2008 require marking of all slag with more than 0.1% of any of Ni and Co as potentially hazardous materials. It then requires the end user of the material to perform a risk analysis: this would impair or even prevent reuse of such slag in most known applications.

When smelting a metallurgical feed material containing Co and/or Ni, the heavy metal content of the slag will generally exceed the above-mentioned limits. For example, elwert et al (World of Metallurgy-Erzmetal, GDMB-Medienverlag, clausthal-Zellerfeld, vol.65, vol.3, pp.163-171, 2012) illustrate this, and discuss three exemplary slags and their detailed phase compositions.

By increasing the level of reduction, it is possible toThe total Ni and Co content of the slag is further reduced to less than 0.1%. However, these reduction reactions are endothermic and, more importantly, require a reducing agent, which is most typically carbon-based. The desired level of reduction means that C is burned to CO, not CO ₂ . This limits the enthalpy available for heating and melting the metallurgical feed material to a large extent, thereby requiring the use of additional heating means.

WO2018073145 teaches the addition of Co-containing materials, such as batteries, to Cu or Ni reformers. The feed comprises mainly copper matte, i.e. metal sulphide. As is typical in reformer furnaces, the smelting heat is oxidized from S to SO ₂ And (3) generating. The enthalpy of the reaction is used to smelt a limited portion of the cells and sulfiding feed.

WO2011035915 describes a high temperature process for treating spent Li-ion batteries, which produces Co-, ni-and Cu-containing alloys and slag. Energy is provided by the oxidation of Al and C in such cells, which corresponds to a spontaneous smelting process. To ensure such spontaneous processes, WO2011035915 teaches that the percentage of spent batteries in the total feed needs to be higher than 153% -3.5 (al+0.6c), where Al and C are weight% of Al and C in the battery. The main source of Al in the cell comes from the casing material. Spontaneous smelting according to this disclosure can only be achieved when the cells are predominantly present in the total feed and when the cells contain high concentrations of Al and/or C.

Recently, new designs of battery packs using the so-called battery-to-battery technology (CTP) have become more prominent in the market. The battery pack using this technique is characterized by a significantly lower Al content. Mathematically, the above formula requires the addition of more than 100% of the cells in the feed. Therefore, such a lean Al cell is not possible to spontaneously smelt.

Other methods may be used to smelt these types of batteries. For example, WO2016023778 uses an electrical plasma to provide the additional energy required to smelt the battery. The additional energy of course results in higher costs. Another disadvantage of this method is the high impurity content of the alloy. This is also observed in WO 2011035915.

From EP2677048 a 2-step smelting process is known for recovering metals from spent Li-ion batteries. It teaches the formation of an impure alloy in a first step of strong reduction followed by purification in a second step of oxidation. The first step is neither energy efficient nor spontaneous.

The invention discloses a substitute 2-step smelting method for optimizing energy requirements. Smelting conditions allow spontaneous smelting in the first step, even in the case of scrap batteries with low Al and C content.

This result is achieved by better utilization of chemical energy in the waste battery. For this purpose, the process conditions in the first smelting stage are selected so as to oxidize C to CO ₂ . This is quite different from the known methods in which strong reducing conditions mean that C is only oxidized to CO. Oxidation to CO ₂ In effect, more exothermic, provides the energy required to melt the entire battery, even when it contains a different composition than the waste battery.

Some Ni and Co will sink into the slag due to the oxidation conditions of the first step. Therefore, a second step of slag reduction cleaning is required. This second step is performed only on slag that preferably remains in a liquid state and requires only a very small amount of energy. Thus, the combined total energy requirement of the 2 steps is more advantageous than a single-step smelting process.

According to a first embodiment, recovering valuable metals from a metallurgical feed comprising a slag former, a Li-ion battery comprising Co, ni, metallic Al and C, or a derivative thereof, comprises the steps of:

-providing a device for immersion implantation of O-containing ₂ A metallurgical furnace of a plant for gas;

-defining an oxidation level Ox characterizing the oxidation smelting conditions according to the formula:

Ox＝pCO ₂ /(pCO+pCO ₂ )，

wherein 0.1<Ox<1, pCO and pCO ₂ CO and CO in contact with the melt ₂ Is a partial pressure of (2);

-preparing a metallurgical feed comprising a weight fraction Bf of a Li-ion battery or derivative thereof according to the formula:

1>Bf>0.3/((1+3.5*Ox)*C)+2.5*Al)，

wherein Ox is the oxidation level and Al and C are the weight fractions of the metals Al and C, respectively, in the cell or its derivative;

by injecting O-containing into the melt ₂ Oxidizing smelting said metallurgical feed material with a gas to a defined oxidation level Ox, thereby obtaining a first alloy comprising mainly Ni and a first slag containing residual Ni and Co;

-liquid/liquid separation of the first alloy from the first slag; and

-subjecting said first slag to a reduction smelting with a heat source and a reducing agent, maintaining a reduction potential, ensuring the reduction of Ni and Co, thereby producing a second alloy, and a second slag having a Ni content of less than 1%, preferably less than 0.5%, more preferably less than 0.1% by weight.

"slag former" means: for example CaO, al ₂ O ₃ And SiO ₂ One or more of the following. Other slag formers well known to the skilled artisan may also be present. The slag forming compounds themselves may be added or they may be obtained in situ from the readily oxidizable metal present in the feed.

By "Li-ion battery or derivative thereof" is meant: new or spent batteries, scrapped batteries, production waste, pre-treated battery material after comminution or sorting. However, the product will still contain appreciable amounts of Co, ni, metallic Al and C.

The "major portion" of an element means: more than 50% by weight of the amount of elements present in the metallurgical feed.

The minimum value of the oxidation level Ox is 0.1, which is calculated by generating a sufficient amount of CO ₂ The need to heat and melt the metallurgical feed material is determined because the production of CO alone is generally insufficient. An upper limit of less than 1 corresponds to avoiding extreme oxidation conditions, which will prevent a major part of the Ni from merging into the alloy during the smelting step. Here it is assumed that CO and CO ₂ Contact with the melt, thereby ensuring control of the redox conditions.

The step of defining the oxidation level Ox with a cell of fraction Bf requires conditions conforming to the formula. Based on the battery composition, it should be verified that the calculated value of Bf is physically feasible, i.e. Bf <1. Otherwise, a higher Ox should be defined up to a value less than 1.

The above operating conditions have been found to be effective for battery fractions Bf greater than 0.3. Below this value, the battery will likely not be able to provide enough energy to allow spontaneous smelting of the total metallurgical feed.

From an economic and ecological point of view, clean slag is important. Although the limits of 1 wt% and 0.5 wt% Ni are based on economics, 0.1% represents an accepted upper limit for reuse of slag in other useful applications.

If the criteria of the formula are met, the order of defining the oxidation level Ox and the steps of preparing the metallurgical feed is not important. Thus, starting from the given cell fraction Bf, the minimum oxidation level Ox can be determined. This reverse order is the object of the second embodiment.

According to a second embodiment, recovering valuable metals from a metallurgical feed comprising a slag former, a Li-ion battery comprising Co, ni, metallic Al and C, or derived products thereof, comprises the steps of:

-using a metallurgical feed comprising a weight fraction Bf of a Li-ion battery or derivative thereof to prepare a metallurgical feed;

Ox＝pCO ₂ /(pCO+pCO ₂ )>((0.3/Bf-2.5. Times. Al)/C) -1)/3.5, wherein 0.1<Ox<1, pCO and pCO ₂ CO and CO in contact with the melt ₂ Al and C are the weight fractions of the metals Al and C, respectively, in the cell or its derivative;

-liquid/liquid separation of the first alloy from the first slag; and

-subjecting said first slag to a reduction smelting with a heat source and a reducing agent, maintaining a reduction potential, ensuring the reduction of Co and Ni, thereby producing a second alloy, and a second slag having a Ni content of less than 1%, preferably less than 0.5%, more preferably less than 0.1% by weight.

In this embodiment, the oxidation level Ox is determined after the feed has been prepared. It should be verified that the Ox calculated values that would allow the desired oxidation and spontaneous smelting conditions are compatible with the oxidation level Ox <1.

It can be demonstrated that the formula of determining Bf from Ox is equivalent to the formula of determining Ox from Bf.

The application of the formulas of the first or second embodiment results in a spontaneous feed, which means that the step of oxidative smelting can be performed by solely utilizing the energy contained in the battery or its derivative. No additional energy is required to be added nor is fuel, coke or other carbon source required nor is reactive compound in the remainder of the metallurgical feed.

For example, in actual operation, a small amount of energy may still be provided for different reasons, such as compensating for abnormally high heat losses of a particular furnace. Such a small amount should preferably be limited to less than 50%, more preferably to less than 10% of the total energy requirement of the first smelting step.

The type of furnace and the exact operating temperature are not important, but the temperature should allow for sufficient smelting of the metallurgical feed material to obtain the first alloy and the first slag. In general, known melters operating at temperatures such as 1350 ℃ to 1800 ℃ are suitable for smelting feeds containing Li-ion batteries or derived products thereof. Preferably above 1450 c to ensure melting of the various input materials, while preferably below 1550 c to limit energy consumption, as shown in the examples below.

Another embodiment according to any of the preceding embodiments is characterized by a spontaneous oxidation smelting step, i.e. using only the energy contained in the battery or its derivative.

Liquid/liquid separation of alloys and slag is very common in the metallurgical industry, for example by so-called "tapping" of the liquid phase from the furnace.

In another embodiment according to any of the preceding embodiments, the slag is maintained in a liquid state between the liquid/liquid separation step and the reduction smelting step.

This ensures that the energy consumed for heating and melting the feed material in the first smelting step is kept to a maximum. If the slag is allowed to cool and solidify, additional energy will be required to remelt it during the reduction smelting step. This additional energy is generally tolerable, especially when the amount of first slag is significantly lower than the amount of total metallurgical feed.

In another embodiment in accordance with any of the preceding embodiments, the catalyst comprises O ₂ The gas being enriched air or pure O ₂ 。

And using air as the O-containing gas ₂ This embodiment produces less heat loss when compared to gases.

In another embodiment according to any of the preceding embodiments, ox <0.98, preferably Ox <0.95.

These conditions correspond to slightly reduced oxidation levels. These may still be sufficient to ensure spontaneous smelting while providing better direct Ni and Co yields in the first alloy.

In another embodiment in accordance with any of the preceding embodiments, the slag former comprises up to 50% CaO, up to 55% Al by weight ₂ O ₃ And up to 65% SiO ₂ 。

Using these guidelines, the skilled artisan will readily obtain slag having a viscosity low enough to allow decantation and phase separation at operating temperatures. The slag former itself may be added or may be generated in situ by oxidation of metals such as Si or Al present in the feed.

In another embodiment according to any of the preceding embodiments, the method comprises the step of transferring the separated first slag to a second melting furnace adapted to perform the reduction smelting step, thereby obtaining a second alloy comprising Ni and Co and a depleted second slag.

Thus, the smelting steps may be performed batchwise with the Ni-Co alloy tapped in between, or they may be performed in two different furnaces.

In another embodiment according to the foregoing embodiment, the second furnace is an electric furnace.

When high temperature, strong reducing conditions are required, an electric furnace is indeed suitable.

In another embodiment according to any of the preceding embodiments, the method comprises a liquid/liquid separation step of the second alloy from the second slag.

The second alloy may be further processed by hydrometallurgical methods to separate and purify the metal. This means that the leaching step, which is preferably performed after atomizing the alloy, is performed.

In another embodiment according to the preceding embodiment, the method comprises the step of recycling the separated second alloy to the oxidation smelting metallurgical feed material, preferably in liquid state.

This embodiment produces excellent overall yields of Ni and Co in the first alloy even when the direct yield of the first alloy is low.

In another embodiment according to any of the preceding embodiments, the method comprises the steps of:

-atomizing the first alloy; and

-dissolving the atomized alloy under acidic conditions, thereby obtaining a metal-containing solution suitable for further wet refining.

The oxidation level of the first step is defined by the parameter Ox, i.e. pCO ₂ And (pCO+pCO) ₂ ) The ratio is defined. In practice, this level will lead to the major part of Ni being incorporated into the first alloy. The residual Ni will sink into the first slag to a concentration of more than 2%, preferably more than 5% by weight in total. This residual slag Ni and any slag Co will be recovered in the second alloy.

According to the above embodiment, the oxidation operating conditions in the first step result in the production of a large amount of relatively pure Ni and Co first alloy that contains little or no other metals, such as Si, fe or Mn. These conditions allow for the complete oxidation of at least a portion of C to CO ₂ Thereby generating the necessary energy to melt the feed material.

The reduction operating conditions of the second step ensure complete recovery of small amounts of Ni and Co in the second alloy. The alloy may be further processed or recycled to the first step, ensuring excellent overall yields of Ni and Co. This second step produces a clean second slag in which Ni is less than 1% by weight. In addition to compensating for heat losses, no too much energy is required, especially when the first slag remains in liquid state.

Too strong reducing conditions in the second step do not have serious adverse effects, but may result in an alloy containing undesirably large amounts of Si and Mn. Si can cause difficulties in downstream processing of the alloy as it relates to filtration problems in hydrometallurgical processing of the alloy. In the second step, mn reduction requires additional energy, so Mn reduction is undesirable in addition to producing clean slag.

Under the direction of the observed characteristics of Co, ni and Mn, the skilled artisan will be readily able to control the extent of reduction by adding a reducing agent such as coal or natural gas.

The following examples illustrate the invention.

Example 1

The metallurgical feed according to table 1 was prepared with 500kg of cells, 80kg of limestone and 20kg of silica. A cylindrical furnace with a diameter of 1m lined with 200mm magnesia-chrome bricks was used.

The feed was continuously fed to the furnace at a rate of 500kg cell/hour while maintaining a bath temperature of 1450 c without additional coke, natural gas or electrical energy. The heat through use rate was 77Nm ³ Immersion O/h ₂ The injection oxidizes Al and C in the cell. These conditions correspond to CO ₂ And (CO+CO) ₂ ) The ratio was 0.30.

After 1 hour, slag (1.1) was tapped from the furnace while allowing the alloy (1.1) to cool. The slag amounting to 188kg, which was fed into the second melting furnace while it was still liquid. For this second step, an electric furnace was used.

Table 1: material balance in the first smelting step

The electric furnace was operated at a temperature of 1500 c and 3.5kg of coke was added to the slag as a reducing agent. A net power of 30kWh was supplied to the electric furnace to maintain the bath temperature.

After 1 hour of reduction and after decantation, slag (1.2) and alloy (1.2) were tapped from the furnace and allowed to cool. The detailed material balance is provided in table 2.

Table 2: material balance in the second smelting step

Example 2 (comparative)

The metallurgical feed according to table 3 was prepared with 500kg of cells, 80kg of limestone and 20kg of silica. A cylindrical furnace with a diameter of 1m lined with 200mm magnesia-chrome bricks was used.

The feed was continuously fed to the furnace at a rate of 500kg cell/hour while maintaining a bath temperature of 1450 c without additional coke, natural gas or electrical energy. For high metal yield, 42Nm is injected ³ O of/h ₂ To achieve the desired degree of reduction. The conditions applied correspond to CO ₂ And (CO+CO) ₂ ) At a ratio of 0.0, i.e. substantially only CO and no CO ₂ . A net power of 220kWh is required to maintain the required temperature.

After 1 hour of reduction and after decantation, slag (2) and alloy (2) are tapped from the furnace and allowed to cool. The detailed material balance is provided in table 3.

Table 3: material balance for single-step smelting

Comparison of example 1 with example 2.

The first alloy (1.1) produced in example 1 contained fewer impurities than the alloy (2) from comparative example 2. This is especially the case for C and Mn, where the concentration in example 1 drops below the detection limit of 0.1% compared to 1.2% C and 6.6% Mn. The same is true for Fe, wherein the concentration in the first alloy (1.1) is 4% compared to 6.6% in the alloy (2) according to the comparative example. The high purity obtained according to example 1 will make any hydrometallurgical subsequent treatment of the alloy easier and cheaper.

Furthermore, the difference between example 1 and example 2 is the electrical energy required for the two steps. In example 1, only 30kWh of energy was required to perform the reduction process, as compared to 220kWh in comparative example 2. The two-step smelting process of example 1 requires only 14% of the electrical energy according to comparative example 2.

It should be noted that the specific electrical energy required in the reduction step will be even lower when larger industrial scale furnaces are used. Since the volume to area ratio of the furnace will increase, heat loss will decrease, providing even greater advantages.

Example 3

The metallurgical feed according to table 4 was prepared with 500kg of batteries, 80kg of limestone and 20kg of silica, and 500kg of slag and 100kg of alloy from, for example, other battery recycling operations. A cylindrical furnace with a diameter of 1m lined with 200mm magnesia-chrome bricks was used.

Table 4: material balance in the first smelting step

The feed was continuously fed to the furnace at a rate of 500kg cell/hour while maintaining a bath temperature of 1450 c without additional coke, natural gas or electrical energy. Heat is applied by using submerged 140Nm ³ O of/h ₂ The Al and C in the battery are oxidized to provide. These conditions correspond to CO ₂ And (CO+CO) ₂ ) The ratio was 0.85.

After one hour, the alloy (3.1) formed is tapped from the furnace and allowed to cool. A total of 922kg of slag (3.1) is tapped and charged into the second furnace while it is still liquid. For this step, an electric furnace was used.

The electric furnace was operated at a temperature of 1500 c and 45kg of coke was added to the slag. After 1 hour of reduction and after decantation, the alloy (3.2) and slag (3.2) were tapped from the furnace and allowed to cool. The detailed material balance is provided in table 5. A net power of 190kWh was supplied to the electric furnace to maintain the bath temperature.

Table 5: material balance in the second smelting step

This example illustrates that the process allows for spontaneous operation even when the bulk feed contains other components than a battery. However, a higher degree of oxidation is required: in example 3, the ratio was 0.85 as compared to 0.30 in example 1. This produced a first alloy (3.1) rich in Ni and lean in Fe. These specifications are advantageous. However, the Ni and Co yields of the first smelting step are lower. This lower yield can be substantially compensated by recycling the alloy from the second smelting step to the first smelting step.

Example 4

Li-ion cells having the composition shown in table 6 were smelted in a cylindrical furnace with a diameter of 1 meter lined with 200mm magnesia-chrome bricks according to the invention.

A metallurgical feed comprising 180kg of limestone and 150kg of silica as fluxes and 500kg of Li-ion batteries was prepared.

The mixture was continuously charged to the furnace at a rate of 500kg cell/hour and maintained at 1350 ℃ bath temperature without coke, natural gas or electricity. Energy is obtained by using submerged O ₂ Injecting Al and C oxygen into the batteryAnd (3) chemical supply. For the feed shown in Table 6, 91Nm was injected ³ O per hour ₂ . These conditions correspond to CO ₂ /(CO+CO ₂ ) The ratio was 0.45.

After 1 hour, the phases were tapped from the furnace. The alloy (4.1) is allowed to cool. The slag (4.1) amounts to 400kg and is fed into the second melting furnace while it is still liquid. For this second step, an electric furnace was used.

Table 6: material balance in the first smelting step

After the first step, the slag was separated and transferred to an electric furnace at a temperature of 1500 ℃ with 10kg coke and 400kg slag added per hour. After 1 hour of reduction and decantation, the alloy and slag were tapped from the furnace and allowed to cool. The detailed material balance is provided in table 7.

Table 7: material balance in the second smelting step

Example 5

The metallurgical feed according to Table 8 was prepared with 500kg Li-ion battery, 100kg limestone and 40kg silica. A cylindrical furnace with a diameter of 1m lined with 200mm magnesia-chrome bricks was used.

The feed was continuously fed to the furnace at a rate of 500kg cell/hour while maintaining a bath temperature of 1550 ℃ without additional coke, natural gas or electrical energy. The heat through use rate was 77Nm ³ Immersion O/h ₂ The injection oxidizes Al and C in the cell. These conditions correspond to CO ₂ And (CO+CO) ₂ ) The ratio was 0.30.

After 1 hour, slag (5.1) was tapped from the furnace while the alloy (5.1) was allowed to cool. The slag amounting to 188kg, which was fed into the second melting furnace while it was still liquid. For this second step, an electric furnace was used.

Table 8: material balance in the first smelting step

The electric furnace was operated at a temperature of 1500 c and 3.5kg of coke was added to the slag as a reducing agent.

After 1 hour of reduction and after decantation, slag (5.2) and alloy (5.2) were tapped from the furnace and allowed to cool. The detailed material balance is provided in table 9.

Table 9: material balance in the second smelting step

Conclusion:

examples 4 and 5 show spontaneous processes with different temperatures for the first smelting step.

The fraction of feed cells used was compared to the minimum cell fraction (Bf) required for spontaneous smelting, using cell composition and oxidation level, ox=pco ₂ /(pCO+pCO ₂ )

1>Bf>0.3/((1+3.5*Ox)*C)+2.5*Al)

The cell fraction for example 4 was 60% whereas spontaneous smelting required 59%. Thus, example 4 shows the minimum cell fraction required for spontaneous smelting at a given cell composition and selected oxidation level. The process is operated at 1350 ℃ sufficient to keep the slag and alloy liquid.

The cell fraction for example 5 was 78% whereas 69% was required for spontaneous smelting. Thus, example 5 uses a higher cell fraction than the minimum required for spontaneous smelting and the process is operated at 1550 ℃.

Claims

1. A method of recovering valuable metals from a metallurgical feed comprising a slag former and a Li-ion battery or derivative thereof comprising Co, ni, metals Al and C, the method comprising the steps of:

Ox＝pCO ₂ /(pCO+pCO ₂ )，

1>Bf>0.3/((1+3.5*Ox)*C)+2.5*Al)，

-liquid/liquid separation of the first alloy from the first slag; and

2. A method of recovering valuable metals from a metallurgical feed comprising a slag former and a Li-ion battery or derivative thereof comprising Co, ni, metals Al and C, the method comprising the steps of:

-using a metallurgical feed comprising a weight fraction Bf of a Li-ion battery or derivative thereof to prepare the metallurgical feed;

-liquid/liquid separation of the first alloy from the first slag; and

3. The method of claim 1 or 2, wherein the oxidising smelting step is spontaneous.

4. The method defined in any one of claims 1 to 3 wherein the first slag is maintained in a liquid state between the liquid/liquid separation step and the reduction smelting step.

5. The method of any one of claims 1 to 4, wherein the O-containing ₂ The gas being enriched air or pure O ₂ 。

6. The method according to any one of claims 1 to 5, wherein Ox <0.98, preferably Ox <0.95.

7. The method of any one of claims 1 to 6, wherein the slag former comprises up to 50% CaO, up to 55% Al by weight ₂ O ₃ And up to 65% SiO ₂ 。

8. The method according to any one of claims 1 to 7, further comprising the step of transferring the separated first slag to a second melting furnace adapted to perform a reduction smelting step, thereby obtaining a second alloy comprising Ni and Co and a depleted second slag.

9. The method of claim 8, wherein the second furnace is an electric furnace.

10. The method of any one of claims 1 to 9, further comprising a liquid/liquid separation step of the second alloy from the second slag.

11. The method according to claim 10, further comprising the step of recycling the separated second alloy to the spontaneous smelting step, preferably in liquid state.

12. The method according to any one of claims 1 to 11, further comprising the step of:

-atomizing the first alloy; and